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MQ-3 Alcohol Sensor with Nokia 5110 LCD Module.
What is MQ-3 Sensor?
Mq3 is a sensor which measure alcohol sensitively. The sensor has 6 pin (it can be changed sensor version or brand, I worked on 6pin MQ-3 sensor)
Heater pins are represented by h.
You need supply 5VDC h pin and of course other h pin must connect to ground. (No need any resistor)
You have to connect 5VDC to the A pin. It can be same voltage and voltage source like h pin.
The most important part is B pin. Because you have to measure Analog (code:AnalogRead();) values. And connect Analog pin and B pin. B pin must connect ground but you have to use resistor. It can be change 2K and 20K ohm. (I used 10K resistor)

MQ-3 Paint Sketch

MQ-3 Paint Sketch

Note: There is no difference A and B pins. The naming can be changed.Important note: The sensor may not work first 24-48 hours. –read datasheet preheat time. You should let it warm up.You can see datasheet MQ-3 here;